"These workforce projections will provide timely information to policymakers and advocates at the state level, giving them a better sense of different forces that will affect the future needs of primary care physicians," said Stephen Petterson, Ph.D., senior health policy researcher for the Graham Center.

The projections rely on a combination of factors to gauge current and future workforce needs on a state-by-state basis, focusing heavily on increased patient demand that is likely to result from

an aging population,

overall population growth and

coverage expansions due to the Patient Protection and Affordable Care Act.

For example, according to the projection for Arizona(www.graham-center.org), the state will need an additional 1,941 primary care physicians by 2030, a 50 percent increase from the state's current number. Of this total, 1,466 primary care physicians are needed because of population growth, 360 because of increased utilization, and 115 because of insurance expansions that occur as part of the Affordable Care Act.

"With these projections, people can understand the different sources for the increases. There is no mystery behind it," said Petterson.

Each state workforce brief is illustrated with graphs showing the current number of primary care physicians in the state and the projected number of primary care physicians each state will need every five years for the next 25 years. Another graph shows how the demand for primary care physicians in a particular state compares with the demand for primary care physicians in that state's region and the nation as a whole.

The projections demonstrate the differences that exist among the states in terms of workforce needs, Petterson said. In some states, populations are rapidly increasing, and in other states, population growth is much slower or even declining, creating much different workforce needs in the various states.

According to the Graham Center, the projections are based on calculations that are not "set in stone." For example, the nation's immigration policies will play a large role in driving future population growth in certain states, thereby determining how many primary care physicians are needed, Petterson said.

"Imagine, if we close the borders or lessen restriction on immigration -- those kinds of changes could throw the projections off," Petterson said.